466 PROF. W. S. BOT7LTOX ON THP: [XoV. 1904, 



measuring up to O05 inch across, with simple and lamellar 

 twinning, and an extinction-angle up to 16°. 



Xo. 201(3) is a buff rock with pink grains, which microscopically 

 shows decomposed glassy particles and many broken crystals of 

 felspar (0*05 inch), parts of short rectangular prisms with albite- 

 lamellation. A lapillus, O03 inch across, is much stained with 

 red iron-oxide and is crowded with minute felspar-laths. 



In among these tuffs the coarsely-amygdaloidal intrusive dolerite 

 has made its way. Xo. 20]/ 1 ) is a fine-grained, granulitic dolerite 

 with serpentinized oliviiie-phenocrysts, in general character similar 

 to Xo. 28, described on p. 481. Xo. 201 y is a somewhat doubtful 

 rock. It is dull yellowish-green, fine-grained, with green needles and 

 larger greenish-black patches with a dull pitchy lustre, made up of 

 a soft substance which is greenish-yellow when scratched — probably 

 palagonite. Microscopically, it is of uneven texture and colour, 

 with small laths of cloudy plagioclase, milk-white in reflected light, 

 occurring ophitically with pale-green, much-cracked augite, altering 

 to a dark-green chloritic mineral. There is a good deal of pale-green 

 and yellow substance,, with cracks that suggest olivine, and red, 

 slightly-pleochroic deposits in small tlakes and needles along the cracks. 

 The description of this rock would seem to apply equally well to 

 the ophitic dolerite with serpentinized olivine, and the andesite-lava 

 with patches of palagonitized glass. On the whole I am inclined to 

 put it in the latter group (see p. 471). 



At (434), in a small opening near the road, is a dull purplish- 

 red, fine-grained rock, which, microscopically, is seen to be much 

 stained yellow, brown, and black, and made up of minute angular 

 chips of felsite and quartz, in a fine brown dust. Fragments 

 measuring O'l inch across, composed of these chips, are embedded 

 in a matrix of the same materia], with crystals in nests or clusters, 

 the whole showing traces of bedding. This rock is distinctly more 

 acid-looking than the palagonite-tuffs just described, and shows a 

 temporary return to the more acid type which follows the Xorthern 

 Ehyolite. 



A conspicuous crag on the south-west of the gulley, referred to 

 as ' Agglomerate-Crag ' in my field-notes, is made up of a coarse 

 andesite-agglomerate or tuff, but very varied in colour and texture. 

 Some parts consist of yellowish-green palagonite-tuff with minute 

 angular dark-grey patches, with a flaggy and slightly-schistose struc- 

 ture, crumbling readily when struck with a hammer, others being of 

 harder, fine-grained, pink and green, gritty tuff; or again extremely 

 fine-grained, purple, yellow, or green halleflinta. Angular fragments, 

 sometimes several inches across, of purple amygdaloidal andesite, 

 often showing most pronounced fluxion-banding, are embedded in a 

 green or pink, fine-grained matrix. The entire crag is much 

 jointed, the fragments showing elaborate faulting on a small scale, 

 and epidote and chlorite are common as secondary products. 

 Immediately behind the main crag, the tuff, with banded and 

 vesicular purple andesite-lapilli, embedded in a fine matrix of the 



